Harvest management - Ecological Applications: Toward a Sustainable World - page 173

appreciate that the maximum sustainable yield may be harvested by fi xed quota, fi xed effort or
constant escapement strategies, with varying levels of administrative expense and risk of 'getting
it wrong'
understand that the most realistic harvest models recognize that different age classes have differ-
ent mortality rates and contribute differentially to reproduction
appreciate that harvesters exert a profound selection pressure that can cause evolution to smaller
size-at-maturity, with implications for sustainable yields
recognize that management recommendations differ when the objective is expressed in terms of
profi t rather than size of harvest
appreciate that sociopolitical factors often come into play when governments make decisions about
harvest management

7.1 Introduction Elena, a Guatemalan, remembers when forest harvesting was a free for all. ' Before

1950 we tapped latex from chico trees - that's what they make chewing gum from. Later
some foreign companies were allowed to cut down our mahogany trees - they made big
money but most of the forest is now gone. We were heartbroken about the loss of the
mahogany. But many of us were also unhappy when some international conservation
organizations got involved and imposed their rules on us. ' That was about 25 years ago.
There was a lot of resentment and some engaged in illegal logging at that time. But
the government listened to local opinion and now, together with 75 other families,
Elena has what they call a community forestry concession. ' And, guess what? We have
been granted Forest Stewardship Council Certifi cation so that people know that what we
sell comes from a forest that is cared for. The area we manage is more than 10,000 hec-
tares but we harvest from just 400 hectares a year. We take only some of the bigger trees
(wider than 55 cm) including mahogany, but never more than two from each hectare. It's
great to be working for ourselves, in our own forest ' . Elena is proud of what her com-
munity is achieving.

7.1.1 Avoiding the
tragedy of the
commons

We all depend on the har vesting of living resources, whether these are domesticated
(c abbage s, pl ant at ion trees, beef cattle) or wild (natural forest trees, bushmeat,
marine fi sh). Sustainable harvesting is a primary aim of resource management, so
future generations can enjoy the same opportunities as we do. And achieving sus-
tainability does not always pose a diffi culty. A producer of cabbages, for example,
has simply to plant an appropriate number of seeds, take care of the growing plants
and harvest the entire crop to take to market for the highest economic returns. Much
the same applies to foresters when they 'clear-cut' a plantation of trees. And the same
can be said for a fi shing club that 'seeds' a pond with trout reared in captivity for
the enjoyment of anglers during a brief fi shing season, or a game hunting company
that releases captive reared animals into the gun sights of its clients. As long as the
economic returns justify the costs, these activities are sustainable - because although
all the plants and animals die in the process, suffi cient seeds, fi sh and game can be
reared and reintroduced into the exploited ecosystem.
Things become trickier when the plants or animals live and reproduce in the wild.
Thus, foresters who harvest natural forests have a more complex situation on their
hands because suffi cient trees of various ages need to remain untouched so that
harvests for future generations are protected. In their favor, the foresters know the